Rotating drilling heads employ elastomeric sealing elements to effectuate a seal between a rotating drillstring and the stationary head. The elastomeric sealing element is mounted on bearings that allow the sealing element to rotate with the drillstring. In most conventional drilling operations, the drilling head is positioned below the drill floor and above the blowout preventer. The drilling head operates to divert pressurized drilling fluids, and other materials flowing up through the wellbore, away from the drill floor.
In rotary drilling operations, the drillstring is rotated by a kelly drive or a top drive. A kelly drive engages a faceted member of the drill string, or kelly, that is connected to the drillstring. The kelly drive is often powered by a rotary table on the drill floor. Many rotating drilling heads are configured to be rotated by interfacing with the kelly either directly, or through a mechanical interface.
Top drive drilling systems rotate the drillstring using an electric or hydraulic motor mounted directly to the top of the drillstring. In top drive drilling systems no kelly is used and the rotating drilling head has to rely on the friction contact between the sealing element and the drillstring to rotate the sealing element. This friction contact is often insufficient to cause sufficient rotation of the sealing element, resulting in relative rotary motion between the drill pipe and the sealing element. A relative rotary motion between the sealing element and the drill pipe can lead to excessive wear in the sealing element, thus reducing the effective life of the seal.
Accordingly, there remains a need to develop methods and apparatus for rotating the sealing element of a rotating drilling head that overcome certain of the foregoing difficulties while providing more advantageous overall results.